A standard prefilled medicament container--a standard syringe or a so-called carpule.RTM. (Cook Laboratories Inc.)--has a hollow body having an open mouth defining an axis, a pierceable plug or membrane engaged over and sealing the mouth, a ring engaged around the mouth and over the plug and formed with a hole through which an outer surface of the plug is exposed, and a removable cap engageable around the mouth over the ring and plug. For use the cap is removed, the outer plug surface is cleaned, and a needle or cannula is poked through the plug. Then a piston in the body or other means is actuated to express the body's contents through the needle.
Cleaning the outer surface of the plug or membrane is necessary because the cap breathes somewhat and contaminants can get under it onto the surface. Such cleaning is relatively difficult, as the plug outer surface is recessed at the bottom of the hole in the retaining ring.